UFC 155 takes place Dec. 29 and is expected to feature a
heavyweight title rematch between reigning champion Junior dos
Santos and ex-kingpin Cain
Velasquez. A venue has not yet been announced for the event,
but the show will take place in Las Vegas and air live on
pay-per-view.

Leben, 32, was handed a year-long suspension by the UFC after
failing his drug test at UFC 138 this past November. “The Crippler”
faced Mark Munoz in
that encounter, falling by second-round technical knockout after
his corner deemed him unable to answer the call to start round
three. Prior to that defeat, Leben had won four of his last five,
knocking out Wanderlei
Silva in just 27 seconds at UFC 132 after kicking off 2011 with
a UFC 125 stoppage loss at the hands of Brian
Stann.

A former heavyweight, 27-year-old Vemola made the cut to 205 pounds
last year before dropping to middleweight this past May. The
Czech-born competitor made a successful 185-pound debut, choking
out Mike
Massenzio at UFC on Fox 3 prior to stumbling in his most recent
outing against Francis
Carmont, submitting to the Frenchman two months ago at UFC on
Fuel TV 4.